High-pressure studies on nanocrystalline borderline Co_1–xFe_xS₂ (x = 0.4 and 0.5) using Mössbauer spectroscopic and electrical resistivity techniques up to 8 GPa

ABSTRACT

Like bulk, Co_1–xFe_xS₂ nanoparticles also display an anomaly at x = 0.5. The borderline contiguous Co_1–xFe_xS₂ (x = 0.4 and 0.5) nanoparticles were synthesized with colloidal method and characterized for pyrite structure using various techniques, viz., X-ray diffraction, energy dispersive X-ray analysis (EDAX), S K-edge X-ray absorption near edge spectra, transmission electron microscopy (TEM) and Fourier transformed infra-red spectroscopy. The report presents the effect of high pressure on the borderline compositions using the Mössbauer spectroscopic and electrical resistivity techniques. Magnetic measurements on the system showed drastic lowering of Tc due to nanosize of the particles. With increased pressure, quadrupole splitting showed an expected trend of increase to attain a peak representing a second-order phase transition between 4 and 5 GPa for both the compositions. The pressure coefficient of electrical resistivity varied from –0.02 GPa to –0.06 GPa across transition pressure indicating a sluggish nature of transition. This is the first report of pressure effect on nanosized borderline compositions.

KEYWORDS:

• High pressure
• diamond anvil cell
• pyrite
• Fe-doped cobalt disulfide
• Mössbauer spectroscopy
• electrical resistivity

Acknowledgements

Usha Chandra gratefully acknowledges CSIR for awarding Emeritus Scientist grant and UGC for Emeritus Fellowship. She appreciates the help of Dr Manoj Kumar, Ms Payal Rampuria during sample synthesis. She also acknowledges Department of Condensed Matter Physics and Materials science, TIFR, Mumbai for the magnetic measurements. Facilities provided by FIST and DRS programs of the Department of Physics as well USIC, University of Rajasthan are also acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Authors are grateful to council of Scientific and Industrial Research (CSIR), PLANEX program of Indian Space Research Organization, Department of Space (Government of India), Ahmedabad (UC), CSR-SHORe-PSC-02005 and ISRO projects (GP) for funding. UC acknowledges USER-project NEXAFS 56 for funding to perform XANES measurements at INFN-LNF DAFNE synchrotron facility at Frascati (Italy) supported by the collaborators Drs. A. Ballerna, I. Zuburtikudis and K. Asokan.